1. Field of the Invention
Aspects of the present invention relate to a computer and a control method thereof, and more particularly, to a computer having improved power efficiency and a control method thereof.
2. Description of the Related Art
Advanced Configuration and Power Interface (ACPI) is an open solution which is applicable to computer hardware, operating systems (OS), software and peripheral device interfaces. This open solution assists operating systems, hardware and peripheral devices, which are developed by Intel Inc., Microsoft, and Toshiba, to communicate with one another during power utilization.
In a conventional computer, a power management system operates on the basis of a basic input/output system (BIOS), so that parts of the computer should have a non-operation period before the computer is disconnected from a power supply. A primary goal of the ACPI is to enable an OS to include Operating System Directed Power Management (OSPM), which manages overall power activities, thereby providing the parts of the computer with power only when power is needed for the computer to operate correctly.
The ACPI announced in 1996 defines operation modes related to the power state of a CPU as C0, C1, C2 and C3. Here, the C0 state is defined as a normal state, the C1 state is defined as a halt state, the C2 state is defined as a stop-grant state, and the C3 state is defined as a stop clock state.
The CPU performs a minimum operation, such as snooping, to keep a cache relationship in C2 state. In the C3 state, which is also defined as a deep sleep mode, since an external clock is not supplied to the CPU, overall operations of a processor are stopped except for the function of maintaining data, which is stored in the cache memory of the CPU. Accordingly, less power is consumed in the deep sleep mode than in the C2 state.
Recently, Intel Inc. has developed Intel mobile voltage positioning II (IMVP II) as an improved voltage regulation technology which adopts C4 as a new power mode of the CPU, i.e., a deeper sleep mode. In this deeper sleep mode, a voltage level of power supplied to the CPU is lower than the voltage level of power supplied to the CPU during the C3 state, thereby minimizing power consumption while the CPU does not operate.
A conventional computer includes a power source, such as a battery or an adapter, a CPU, and a CPU driving power generator, which generates CPU driving power from source power which has been outputted from the power source. The CPU driving power generator, which is provided in the conventional computer, includes a switch. Due to this switch's switching operation, this switch causes switching loss and conduction loss to occur. Since the conduction loss is proportional to the current level, the conduction loss increases as the current level increases. Thus, the switching loss takes a large portion of the whole loss in the CPU driving power generator in case of a low level of current, thereby giving a great effect in lowering power efficiency. The CPU driving power generator provided in the conventional computer generates the CPU driving power from the source power, which outputs a high voltage from the power source regardless of the current level, thereby lowering power efficiency.